RFID (Radio Frequency Identification) has attracted attention as a scheme for identifying and managing persons and things by using ultra-small wireless radio chips. In a RFID device, an ultrasmall tag (i.e., RFID tag) stores therein data for performing identification by communication with a reader device via either electric waves or electromagnetic waves. The RFID tag is comprised of an IC chip which stores therein information such as an ID code of itself, and has an ability to use electric waves to transmit and receive information to and from a management system. In recent years, battery-less tags are commercially available by virtue of techniques for non-contact power transmission from the antenna side.
Regarding radio IC tag circuits and devices, JP-A-2000-299440 discloses therein a high-frequency operable voltage generator circuit which is designed to give electric power to an SOI (silicon-on-insulator) structure MOSFET by way of a resistor to thereby preclude influence from a parasitic-coupling diode.
Additionally JP-A-8-335709 discloses therein a technique for reducing a threshold voltage by providing an electrical connection in such a way that the gate of a MOS transistor formed on an SOI substrate is kept identical in potential level to a substrate as taken through an n+ diffusion region. It further discloses that etching is done up to an SiO2 film with etch stop applied thereto during chemical etching, for electrical separation of the MOS transistor on the same supporting substrate to thereby form a MOS transistor having air-isolation. There is also disclosed a technique for providing a connection so that the gate-substrate potential is equal to the potential of a drain, thereby causing it to have rectification characteristics for fabrication of a diode bridge or a mixer.
On the other hand, an object of the present invention is to extend the communication distance of a radio IC tag chip. In particular, by applying it to radio IC tag chips which have no internal power supplies and are operable with electric power as received from a reader/writer, it is possible to obtain superior effects and advantages.